## RAID > Redundant Array of Independent Disks - Is not a backup - If your operating system or software, rather than the hard disk, corrupts your data, this corrupted data is sent to both disks and simultaneously corrupts both drives. ### RAID 0 - ![[2022-03-12-15-04-25.png]] - Striping (Disk A and B contain data split between them that together forms the whole) ### RAID 1 - ![[2022-03-12-15-02-23.png]] - Mirroring (Disk A and B are exact copies of each other) ### RAID 10 - ![[2022-03-12-14-20-16.png]] - Combination of [[RAID#RAID 0]] and [[RAID#RAID 1]] - Requires at least 4 drives - Drives should be identical (The disk geometry (number of heads, cylinders, etc.) is critical and it is strongly recommended NOT to use dissimilar disks.) - Protects you from a single drive failure - reads the surviving mirror and stores the copy to the new drive you replaced. (Not nearly as taxing of an operation as [[RAID#RAID 5]]) - cuts your usable disk space in half 4x2TB Disks == 4TB total storage ### RAID 4 - ![[2022-03-12-16-31-20.png]] - consists of block-level striping with a dedicated parity disk. - As a result of its layout, RAID 4 provides good performance of random reads - while the performance of random writes is low due to the need to write all parity data to a single disk ### RAID 5 - ![[2022-03-12-15-10-33.png]] - When a drive fails - it needs to read everything on all the remaining drives to rebuild the new, replaced disk (A heavy load for the surviving disk and potential failure point of the 2nd disk) - Storage Volume ((Number of hard drives - 1) x storage capacity of the smallest hard drive) - 3x1TB drives == 2TB storage, 3rd disk is for parity data - Only at risk for failure if at least 2 drives fail simultaneously - That’s why, typically, an odd number of data carriers, i.e., three, five, seven, etc., is combined. ### RAID 6 - ![[2022-03-12-14-49-20.png]] - Combines four or more hard drives into a single logical drive. - Often referred to as “RAID 5 expansion” - Striping (All data is divided into blocks and distributed evenly to the participating hard disks.) - Parity (always saves two sets of parity information. In that way, associated data can be restored if one or two disks fail.) - Storage Volume ((Number of hard drives - 2) x space of the smallest hard drive) - For example, with four 1GB hard disks, only 50% of their potential memory would be available to store user data. However, as the number of disks increases, this relationship between capacity and parity improves. - Advantage over [[RAID#RAID 5]]] - parity information to recover lost data is saved in duplicate. Duplicated parity data is a more efficient way of creating redundancy, and also ensures higher reliability. - This is less taxing on the remaining drives compared to ordinary ### RAID 50 - ![[2022-03-12-16-28-30.png]] - Minimum of 6 drives ### RAID 60 - ![[2022-03-12-16-30-23.png]] ## Storage via ZFS See [[Zettabyte file system|ZFS]] ## RAID-Z - [ ] TODO https://www.diskinternals.com/raid-recovery/what-is-raidz/